Question(s) about wireless-n router

So today I got a second laptop and now I have 2 laptops, a desktop and my 360. The desktop is wired to my WRT54g and everything else is wireless. I use a Linksys Wireless-N gaming adapter for the Xbox 360. There is a noticeable amount of lag on Xbox Live now when I'm playing and the gf is on one of the laptops. It's obviously even worse when I try to be on OT at the same time on my laptop.

So if I get one of those dual-band Wireless-N routers, I'm 99% positive the laptops and 360 could all work from it. But would this benefit the 360 at all? I'm lost trying to figure out the 2.4ghz and 5ghz band thing, but I looked up specs on both the laptop's wireless adapters. Neither of them list anything about compatibility with 5ghz. But obviously my gaming adapter is compatible, so would that mean it could operate in a different range than the laptops, simultaneously, and not (hopefully) lag at all?